Issue with COMPOUND including REFERENCE

[kmuehlbauer]

A major building block of NetCDF4 format is the use of HDF5 dimension scales.

A NetCDF4 dimension is characterized in HDF5 as a DATASET with an ATTRIBUTE of type STRING with name CLASSand a DATASPACE with DIMENSION_SCALE as data content. Furthermore this DATASEThas an ATTRIBUTE REFERENCE_LIST which dumps like this:

ATTRIBUTE "REFERENCE_LIST" {
  DATATYPE  H5T_COMPOUND {
     H5T_REFERENCE { H5T_STD_REF_OBJECT } "dataset";
     H5T_STD_U32LE "dimension";
  }
  DATASPACE  SIMPLE { ( 1 ) / ( 1 ) }
  DATA {
  (0): {
        DATASET 111195198694608 "/subgroup/y_var",
        0
     }
  }
}

For some reason we can work with REFERENCE as attributes (dereferencing works), but this special REFERENCE inside COMPOUND doesn't work. I'm trying to create some MCVE but still failing to do so. Over at h5netcdf just one test fails, returning wrong values. But the issue is that pyfive can't correctly return the two values from the above example dump (the REFERENCE and the number 0).

I hope that @bnlawrence can make something out of my ramblings. I'll try to come up with an MCVE.

[bnlawrence]

Argh. Dimension scales are my kryptonite, and I've got a couple of weeks of meetings ahead of me. I'll try and have a look, but it might take a while.

[kmuehlbauer]

@bnlawrence I think I've found a solution, currently implementing. This will also bring our compound type to full force. I'll give an update later today.

[kmuehlbauer]

@bnlawrence I can at least take the pressure from you now. I have successfully implemented the COMPOUND type attributes with nested references. It's a bit hacky now. I'll clean up later and might be able to finish this up in the evening.